Project Euler Problem 28

Project Euler Problem 28 solution would be to fold the sequence of rectangles 1 to 500 each yielding its four corner numbers to the accumulated sum:

let problem028 () =
    [1..500]
    |> List.fold (fun (accum, last) n ->
            (accum + 4*last + 20*n, last + 8*n)) (1,1)
    |> fst

How amazingly compact!

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